This invention relates to tire chains. More particularly, the present invention relates to tire chains used on compact front-end loaders and other similar construction machinery to improve floatation, traction, and handling during operation.
For many years cars, trucks, and other tire mounted vehicles have used tire chains to improve operational control over soft or slippery road surfaces.
A. Skid Steer Loaders
More recently, construction machinery owners have attempted to use tire chains on tire mounted construction machines. This is especially true for compact front-end loaders, which will be referred to as skid steers. Skid steers are powerful compact loaders used to dig, haul, or lift earth and other materials. The main components of skid steer loaders include an operator""s cab, a diesel or gasoline engine, hydraulic pumps, hydrostatic transmission, a pair of lift arms, a bucket operatively attached at the 25 distal ends of the lift arms, and two pairs of opposing tires. Many other construction machines and vehicles are composed of similar components. What separates the skid steer from its counterpart construction machinery is its unique steering system.
B. Steering Systems
Front-wheel steering is a popular directional steering system used on tire-mounted vehicles such as cars and trucks. A car usually steers or turns by changing the direction of the front tires. Turning occurs because while being in motion the centerline of the front tires is no longer parallel or in line with the centerline of the rear tires. Similar concepts, e.g. rear-wheel and all-wheel steering, can be seen in typical forklifts.
Many tire-mounted construction machines use articulated directional steering. Articulated steering works because the vehicles are designed in two separate independent sections. The two sections are connected at a pivotal point. Whenever the two sections pivot and their centerlines point in different (unparallel) directions, the vehicle turns. Articulated steering can be seen in most front-end loaders over 10,000 pounds.
C. Steering System for Skid Steer Loaders
The skid steer loaders use a directional steering system. In skid steers, the centerlines of the front and rear tires remain parallel and in line with each other at all times. This kind of steering system can be also seen in excavators, bulldozers and tanks, and is one of the very few steering systems that allow the vehicle to turn 360 degrees without moving forward or backward.
The directional steering capabilities of a skid steer arises from the independent pairs of left and right side drive systems. Tire-mounted skid steers have four axles, two per side of the machine. The two axles per side are spaced typically 3 feet to 4 feet apart on the same lateral axis and evenly protruding from the machine body. Identical wheels and tires are mounted on each of the axles. A key factor for the turning capabilities of skid steer loaders is that the left and right pairs of opposing tires are powered by independent drive systems. As a result, when the left and right pairs of opposing tires are moving forward at the same speed, then the machine moves straight forward. However, if the left pair of tires is moving forward at a different speed than the right pair of tires, then the loader will slide and turn. The machine turns in the direction of the side with the faster moving pair of tires. Moreover, if the left pair of tires is moving forward and the right pair of tires is moving backward, or vice versa, at the same speed, then the skid steer performs a 360-degree rotation without moving forward or backward. Since all four Skid steer tires remain parallel and in line to each other at all times, tire chains can be utilized more efficiently to improve floatation, traction and control.
D. Applying Tire Chains to Skid Steers In the last decade, the skid steer has become a very popular machine in the construction industry. It has won recognition for being a versatile machine (for example, being the construction vehicle with a great variety of attachments), and a compact and maneuverable machine that can handle many types of construction jobs. However, occasionally the tires of the skid steer tend to slip, especially in snow, mud, sand, and other slippery or boggy conditions that are often found on job sites. The insufficient traction of the four skid steer tires under certain conditions results in unsatisfactory and often risky operation and performance. In an attempt to resolve this, tire chains have been applied to skid steers.
When cars or trucks use tire chains, each tire must use its own chain, the so-called xe2x80x9csingle-wheelxe2x80x9d tire chain. Due to the unique steering system of the skid steerxe2x80x94all wheels remaining parallel and in line with each other at all timesxe2x80x94a more advanced tire chain can be used. The skid steer xe2x80x9ctwo-wheelxe2x80x9d tire chain is wrapped around each pair of left and right side tires. The two-wheel tire chain is more efficient because more chain is making contact with the operating ground. The whole area between the two tires on each side of the machine (usually 3 to 4 feet) is used for additional traction and floatation. This feature of the skid steer two-wheel tire chain is in sharp contrast to the single-wheel tire chains, which utilize only the operating ground that is immediately under the tire. Depending on the spread of the wheelbases of the skid steer, the contact area between the operating ground and the two-wheel tire chain can be on average 5 to 10 times greater than that of the single-wheel tire chain.
E. Current Tire Chains for Skid Steer
Current tire chains made for skid steers attempt to solve the problem with traction insufficiency under slippery or boggy operating ground conditions. The main component of the current skid steer two-wheel tire chains is the xe2x80x9cpad.xe2x80x9d The pad usually consists of a crossbar with two opposing sidewalls xe2x80x94one on each side of the crossbar. The sidewalls, which are set perpendicular to the connecting crossbar, create a valley or groove. When subsequent pads are connected together with links to comprise a chain, a continuous groove is formed for skid steer tires to ride within. The sidewalls of each pad keep the chain aligned with the tires and at the same time prevent the tires from derailing off the chain.
F. Drawbacks of Current Two-Wheel Tire Chains for Skid Steers
Current two-wheel tire chains for skid steers generally work mechanically well. However, these tire chains provide poor enhancement to the traction of the loader machine in slippery or boggy conditions and offer little or no floatation. The term xe2x80x9cfloatationxe2x80x9d refers to the wheels and chains of the loader remaining above the ground surface, rather than sinking into the ground during operation of the skid steer. For the optimal performance of the skid steer, both problems of traction and floatation have to be resolved simultaneously. In addition to the traction and floatation problems, the current two-wheel tire chains for skid steers impose many other inconvenient restrictions that need consideration.
One drawback is that current skid steer two-wheel tire chains have a large open space between adjacent pads and between the two crossbars of each individual pad. The open spaces between adjacent pads and between the crossbars of the single pads limits both traction and floatation of the loader. For example, when operating the skid steer in mud, the open spaces within the chain allow the mud to pass upwards. This causes the machine to sink, and creates extreme operating stresses for the drive motors. Indeed, skid steers using the current two-wheel tire chains in mud have to deal with a greater drive motor pressure than not having a chain at all, since the bare tires tend to spin in the mud, while the skid steers with current chains sink into mud. Traction is also lost due to the open spaces. When the chains move and push the mud, the mud simply moves over the crossbars of the pads. When the machine tries to move forward in the mud, the chains whip and mix the mud, instead of effectively pushing it backward and thus creating the thrust necessary to move the machine forward. The same result can be observed while working in sand, pebble and other like materials.
It has been recognized that the origin of problem with the large open spaces in current two-wheel tire chains is in the association with the single-wheel tire chains. The single-wheel tire chains rely on the tire itself to close the open spaces within the chain. The crossbars in the single-wheel tire chains provide only for the enhanced traction, while the tire provides for the floatation. In contrast, in the skid steer two-wheel tire chains in which the contact area between and chains and the operating ground is 5 to 10 times greater, there is currently no mechanism to deal with the floatation problem and, therefore, optimal traction cannot be reached as well.
G. Drawbacks of Current Tire Chains for Skid Steers
While tire chains have been used successfully with skid steer loaders, there are a number of drawbacks associated with such use. During operation of a skid steer with a set of tire chains, the contact surface of all pads wear down as the pads move on the operating ground. The pads eventually break or their limited traction capabilities diminish to an unusable level. The pads are the largest and most costly component of the tire chain. They are difficult and economically unsound to repair. The user has no other choice but to purchase a whole new set of chains, which often come at a considerable cost.
Another major drawback is the destructive nature of the current tire chains when used on concrete, asphalt and similar hard finished surfaces. As mentioned earlier, skid steers have become very popular machines on construction sites. This is especially true for small jobs sites in cities and residential areas where sidewalks, driveways, and asphalt are prevalent. Skid steer tire chains are heavy and difficult to handle, which makes dismantling or assembling a set of chains a time consuming venture that most users prefer to avoid. Damage to the operating ground occurs because the crossbars on each pad are constructed either of steel or cast iron. As the skid steer moves forward, the driving force delivered by the tire chain is usually greater than what the contacting surface can withstand. This causes the surface to scratch, crack or break. As a result, the current skid steer tire chains limit the operating grounds over which the machine may travel or operate, without such damaging drawbacks.
Accordingly, there is a need in the art for low ground pressure tire chains for skid steers to cope with the above-mentioned problems and inconveniences. It is to the provision of such that the present invention is directed.
The present invention meets the need in the art by providing a tire chain for skid steers having spaced-apart pairs of wheels, in which the tire chain comprises a plurality of base units pivotally interconnected in series. Each base unit comprises a pair of opposing ears that each have a portion extending as an interior surface at an oblique angle towards the opposing ear, whereby during operative use of the base unit, a portion of a tire is momentarily wedged in a gap between the side supports. At least one transverse cross-member extends between the ears. The extending portion of the ears each defines a pair of opposing cavities between the extending portion, the ears, and respective laterally outwardly edges of the at least one cross-member. Each of the ears has a port, a cut-out section near the top portion of the ear. The transverse cross-members define a bore within the respective cavities for receiving a fastener. A plate attaches to a lower surface of the cross-members with the fasteners received through the bores. The links pivotally interconnect adjacent base units, for forming an endless-loop track for disposing around a pair of opposing wheels of a skid steer.
Objects, features, and advantages of the invention will become apparent upon reading of the detailed description in conjunction with the drawings, summary, and the claims hereto.
With general reference to the drawings (described below), the present invention overcomes the limitations and restrictions of skid steer tires (14, 16) and current skid steer tire chains that occur both on slippery boggy surfaces and hard finished surfaces. As shown in FIG. 1, the track (12) and base units (24) comprising the track provide the skid steer 10 with an improved apparatus that resolves problems of floatation and traction, wear of the main chain components, and adverse effects on hard finished surfaces. In addition, the present invention stabilizes the maneuverability of skid steer loaders on slopes and enhances the overall control of the machine by the operator.
The track (12) of the present invention comprises multiple components assembled together to form tire chains (12), specifically designed for skid steers (10), but that can also be used on other construction vehicles with similar steering systems. There are five main components and these are called a base (30) (FIG. 2), a shoe (52) (FIG. 2) (and in an alternate embodiment, a rubber shoe (90)) (FIGS. 4, 4A, 4B and 4C), a link (26) (FIG. 3B) (pairs of links are used to pivotally connect adjacent bases to form the track) (FIG. 3A), and a pin (70) (FIG. 3C) to secure the links (26) to the bases (24).
The shoe (52) is a forged steel plate with three grousers (57, 67) which can be attached to the base member (30). The shoe (52) delivers low ground pressure and eliminates large open spaces on the track (12) increasing floatation and traction.
The rubber shoe (90) is a rubber plate with defined traction lugs or grousers (98). The skeleton of the rubber shoe (90) is composed of a forged steel core (92) that bolts on to the base member (30) and: a molded rubber exterior (94). The rubber shoe (90) eliminates open spaces and prevents the track (12) from damaging hard finished surfaces. The rubber shoe (90) provides traction, and allows the skid steer (10) to cross freely over hard surfaces such as concrete or asphalt.
The base member (30) is a cast piece with at least one cross bar (34) and adjacent connecting ears or side supports (32). The base member (30) allows the track (12) to be properly guided on the skid steer tires (14, 16) while connecting all other components together to form a continuous chain or track. The base member (30) is specifically designed to protect the skid steer tire (14, 16) from contacting the connecting parts the links (26), the pins (70), and the shoes (52, 90) during adverse driving ground conditions. In addition, the base member (30) allows the chain (12) to be easily rebuilt. The base member (30) has a 4-bolt pattern to which the shoe (52) or rubber shoe (90) attaches. The base member (30) also has adjustment holes (44, 46 or 45, 47) for connecting links (26) that allows the chain (12) to be tightened or loosened around the tires (14, 16) of the skid steer (10). The base unit (24) enables skid steers (10) using the chain (12) to selectively employ rubber shoes (90) or metal shoes (52) depending on the particular job application. The invention also allows for easy replacement of worn rubber shoes (90) or metal shoes (52) without the need to dispose of the rest of the chain (12), reducing the operational and maintenance costs.
The link (26) is a forged steel piece that connects subsequent base units (24) together forming the continuous chain (12). The link (26) allows the base units (24) to pivot at different angles while operating the skid steer (10) over uneven surfaces.
The pin (70) preferably is a forged steel carriage bolt with a hole (77) made in its ending tip where a cotter pin (79) is inserted. The pin (70) bolts through the base member (30) and the link (26) to attach them together. Although not a preferable solution, the pin (70) can also be made up of a nut and bolt.